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 Question from robert, a student: If (a + b)^2 = 81 and ab = 18, find the value of 1/a^2 + 1/b^2 ?

Robert,

Find a common denominator for $\large \frac{1}{a^2} + \frac{1}{b^2}$ and add the fractions. Compare the numerator to the expanded form of $(a + b)^2$.

Write back if you need more assistance,
Penny

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